The only place I've ever read about low porosity/protein sensitivity is on the nc.com page about properties. My low porosity hair never met a protein it didn't LOVE!! Here's a link to the livecurly/live free page that might help Live Curly Live Free - Curly Hair Basics you a bit more.

If your hair is med/coarse, there may be certain proteins it likes or it may like them all. It's a lot of trial and error.

Whether or not you need a DT after a PT all dcpends on what you use. I use moisturizing, commercial PTs and just use a moisturizing conditioner as my rinse out. Too much protein does show up as dry, strawlike hair. I've never used too much protein, so can't tell you from personal experience. You just won't know until you try.